2oz doesn't sound like much. Is it an exact science? I think simply filling 1/2 - 3/4 of the cone is fine, right? Isn't that enough free space remaining?

Is that marine gear oil easy to find locally? I guess West Marine is a good start to shop?

If you have ever done this you would see 2 oz. is almost 1/3 of the nose cone...The whole deal with this mod is to bathe the bearings,not submerge them...you want just enough oil in there to coat them....if you fill the shit out of it you risk blowing out the front seal....especially when there is no need to fill it that much...

Use a 75w90 with color so you can tell a change from water intrusion.
I change mine with every impeller change/tweak.
Oh, and there's a minute friction loss, which equates to a teeny tiny (probably insignificant) speed gain--but hey, if the other guy isn't doing it, you have that on him.
Just be careful the next time you remove the cone as it will make a hell of a mess if you forget!

Wow, Less than 1/3? The impression i got from other threads was roughly 1/2, while the other 1/2 served well enough for the pressure once hot.

you can put in whatever you feel is neccessary, BUT what is needed is two different things....Like i said you just want to bathe them,not submerge them...think about rotating mass brother and you will figure this riddle out.....